Here is converter between serial port of computer and CASIO diary. This circuit use IO MAX232 which works like converter from 0 to 5V interface on 12V to -12V interface and vice versa. Advantage of this circuit is need of only 5V voltage and he makes needed voltages about +9V and -9V.
Needed voltage for supplying is getted from RTS and DTR signals. There are not needed external power supply. Voltage regulator 78L05 lower voltage for MAX232. Today it's better to use LE50 regulator, which is low drop type. It's better to use schottky diodes. Circuit is recommended from MAXIM catalogue.
Circuit is in connector cover. It's needed cannon 25pin female type connector.
It's better to use plastic cover, not metalized! For connector to diary side we can
use 2.5" JACK type socket. Next we need small piece of wire. We can use two shielded
wires (for headphones) and two 2.5" JACK type connectors. This cable can be used
for communicating between two diaries. Circuit was tested with Amiga500, Amiga1200 and
some PCs on one side and with some CASIO diaries on other side, for example SF-A10, SF-A20,
SF4300.
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